Optogenetics is a relatively new technology in the field of neuroscience that combines genetic targeting of specific neurons or proteins with optical technology for imaging or control of the targets within a neural circuit. Neurons now may be controlled with optogenetics for fast, specific excitation or inhibition within systems as complex as freely moving mammals. Optogenetics is based on the genetic transfection of specific cell types to express photosensitive proteins whose spiking activity can then be precisely controlled by light pulses of specific wavelengths.
Probes are used to take advantage of genetic targeting strategies to express light-sensitive proteins in genetically defined populations of neurons, allowing unambiguous identification of the neurons under investigation. By using light-sensitive probes, it is possible to control the activity of entire populations of potential presynaptic neurons and/or monitor the responses of populations of potential postsynaptic neurons. These optogenetic tools have provided new ways to establish causal relationships between brain activity and behavior in health and disease. While the exploration of the wiring diagram of brain networks is moving forward at an unprecedented scale and steady innovations in optogenetics provide a toolset for identifying and manipulating of circuit components, innovative approaches that enable low-cost, practical solutions for optogenetic tools are lacking. Stimulation through light sources placed on the surface of brain or large fibers placed on the brain parenchyma a few hundred microns away from the recording sites inevitably activates many un-monitored neurons. The Buzsaki Group recently demonstrated a complete optical stimulation and electrical recording system from portable light sources. However, the manual attachment of fibers glued to portable light sources on probe shanks can be highly variable and labor-intensive.
Fiberless optoelectrodes for multicolor neural stimulation
The proposed technology demonstrates the first highly compact, fiberless, monolithically integrated optoelectrode that can deliver multicolor light output alternatively at a common waveguide port using an optical mixer configuration. For the first time it shows successful implementation of efficient end-fire coupling between a side-emitting injection laser diode (ILD) chip and a monolithically integrated dielectric waveguide via a Gradient Index (GRIN) lens onto a neural probe. The integrated GRIN lens offers several advantages over other conventional approaches for smaller scale optoelectronic designs. Moreover, it also provides thermal isolation between light source and waveguide, thus prolonging the total continuous operational time of optoelectrode by at least 10 folds. Such a device can enable independent activation and silencing of neural circuits at a common light port for the first time, thus allowing neuroscientists to study brain activity with unmatched spatial precision and scalability. This approach simplifies packaging, improves noise immunity, and minimizes heat conduction to the end of the probe tips to prevent possible tissue heating at high illumination.
- Improved hardware for investigating cellular contributions to systems neuroscience
- Clinical uses for targeted optical control of neural activity and behavior
- Potential to validate models in identifying symptoms relevant to various neuropsychiatric diseases (e.g. anxiety, depression, schizophrenia, addiction, social dysfunction, Parkinson’s disease, and epilepsy)
- Simplifies packaging
- Improves noise immunity
- Minimizes heat conduction to the end of the probe tips to prevent possible tissue heating
- Better spatial precision